RHEOLOGICAL STUDY OF PHENOLIC RESOL RESINS CURE AFTER GELATION
Advancing the chemical engineering fundamentals
Rheology (T2-4P)
Keywords: Rheology, Resin, Resol, Curing
RHEOLOGICAL STUDY OF PHENOLIC RESOL RESINS CURE AFTER GELATION
J.C. Domínguez, M.V. Alonso, M. Oliet, F. Rodríguez
Departamento Ingeniería Química, Facultad de Química, Universidad Complutense,
28040 Madrid. Spain. Tlf.: 913 944 246, Fax: 913 944 243,
e-mail: jucdomin@quim.ucm.es
Chemorheological curing behaviour of phenolic resol resins after gelation was studied in order to determine their kinetic curing parameters. The curing of thermoset resins is a complex phenomenon which occurs with relevant changes in their rheological properties (1, 2). Phenol-formaldehyde commercial resol resins tested were supplied from Hexion Chemical Iberica S.A. Rheological runs were performed by using an ARES Rheometer with 25 mm parallel plates and 2 mm initial gap. Autotension option was used in order to keep normal forces constant and avoid contact loss between sample and geometry. Isothermal curing runs (80, 85, 90, 95 and 100ºC) were carried out for 30 minutes. Frequency was previously fixed at 1 Hz; therefore, constant frequency test were performance. Linear viscoelastic region (LVR) was determined through strain sweep after isothermal curing to delimit it for each temperature. Applied strain was always inside LVR.
Kiuna model is frequently applied to study the cure stage of epoxy/amine resins (3). In this work a particular case of this method is used to study the cure of the samples after gelation. In Arrhenius model, Andrade equation is proposed to set viscosity dependence on temperature, η0(T). Viscosity increase along curing process is described using a function α defined as Ln(η/η0). Function τ represents the elapsed cure time and the rate of advance of curing process at temperature described by function K(T). Arrhenius model assumes α(τ) as a first order polynomial α=τ. An exponential form equation is used for K(T) model equation. In order to get best fitting model α(τ) was proposed as a second and third order polynomial.
Average activation energy values of 70.21 kJ/mol, 91.32 kJ/mol and 94.80 kJ/mol were found for Arrhenius, second order polynomial equation, and third order polynomial equation, respectively. For α(τ) equation, third order polynomial showed best fitting coefficients and the lowest SQR values.
1. Pascault, J.P.; Sauterreau, H.; Verdu, J.; Williams, R.J.J; “Thermosetting Polymers”. Ed. Marcel Dekker, New York, (2002).
2. Sperling, L.H.; “Introduction to physical polymer science”. Ed. John Wiley Sons, 2nd Edition. Pennylvania, (1992).
3. Kiuna, N.; Lawrence, C.J.; Fontana, Q.P.V.; Lee, P,D.; Selerland, T., Spelt, P.D.M.; Composites: Part A. 33 1497-1503 (2002).
Presented Thursday 20, 13:30 to 14:40, in session Rheology (T2-4P).
